Yes. She was part of American Horror Story. Her presence added a certain charm and talent to the show. She fit into the often dark and complex world of American Horror Story quite well with her acting skills.
I'm not sure specifically. You could try looking at Fantastic Fiction databases or websites dedicated to the genre to find out if there are any works by Jenna Jaxon.
I don't know anything about Jenna's novel because I'm just a big fan of novels and don't have the ability to browse the web. If you have any other questions, I'll try my best to answer them.
Jenna is likely the main character in the story. She could be a young girl, a teenager, or even an adult. Since the story is named after her and the black cat, she's probably the one whose experiences are central to the plot.